need some help calculating mortality w.r.t. whole population

its been a long time since i've done maths...and i need some brushing up on my skills. I find it difficult breaking down the question as to what needs to be answered. Sometimes i don't know which steps need to be taken!
Here is the question:

15% of the members of a population were affected by an epidemic disease. 8% of the persons affected died. Calculate the mortality with respect to the entire population.

if i could get any help, i'd be grateful!

Re: i need some help!

Hi gills:

This looks like a percentage-of-a-percentage problem.

Mortality is usually reported as a rate, but not always "per 100 people" (i.e, a percent). The ratio is often scaled to eliminate "fractional" people.

Like always, whenever we want to work with an unknown or arbitrary number (like the entire population in this problem), we need some symbol to represent it. Let's pick anything.

P = the entire population

15% of this number were affected by the epidemic.

(At this point, I'm going to assume that you understand the use of decimal forms of percents when doing arithmetic.)

The expression 0.15P stands for the number of members in the population that were affected by an epidemic disease.

8% of these people died.

0.08(0.15P) is an expression that represents the actual number of dead. We do the multiplication to simplify this expression.

0.012P

Clearly, this shows the dead as a percent of the entire population. We could report the mortality rate as 1.2%, which means that 1.2 people per 100 died, but maybe it's more meaningful to scale the ratio 1.2/100 by multplying it by 10/10.

The epidemic mortality rate is 12 deaths per 1,000 people in this population.

Cheers,

~ Mark

gills said:

its been a long time since i've done maths...and i need some brushing up on my skills. I find it difficult breaking down the question as to what needs to be answered. Sometimes i don't know which steps need to be taken!
Here is the question:

15% of the members of a population were affected by an epidemic disease. 8% of the persons affected died. Calculate the mortality with respect to the entire population.

if i could get any help, i'd be grateful!

Click to expand...

another way to do this would be to play with some numbers:

Assume the population is 10,000 (since it is % of a % - I took 100[sup:37n8fkxm]2[/sup:37n8fkxm] as the basis number). Then

15% of the members of a population were affected by an epidemic disease

# of people affected by the disease = 0.15 * 10000 = 1500

Then 8% of the persons affected died

# of people died = 0.08 * 1500 = 120

so the ratio of dead (from disease) to total population = 120/10000 <--- What is that as %